Passenger protection device in a motor vehicle with an airbag module

ABSTRACT

The invention relates to a passenger protection device on the steering wheel ( 2 ) of a motor vehicle, comprising a steering wheel airbag module which is arranged behind the cap ( 1 ) of the hub of a steering wheel, containing at least one steering wheel airbag ( 10; 28; 39 ) and at least one gas generator. The hub cap ( 1 ) has a fixed center area ( 8; 21; 29 ) acting as a first wall area around which a second wall area ( 7; 24; 33 ) which is directly adjacent to an edge area ( 12; 23; 31 ) is arranged. When the airbag is activated, an annular gap ( 5 ) can be formed in the second wall area ( 7; 24; 33 ) around the fixed center area ( 8; 21; 23 ), the steering wheel airbag ( 10; 28; 39 ) being embodied in a correspondingly ring-shaped manner with a tubular area ( 11 ) which is associated with the annular gap ( 5 ) and extends therefrom when inflated. According to the invention, the annular gap ( 5 ) can be formed directly around the fixed center area ( 8; 21; 29 ) when the airbag is activated by expanding and/or tearing open at least the adjacent edge area ( 12; 23; 31 ) of the second wall area ( 7; 24; 33 ).

[0001] The invention relates to a passenger protection device in a motorvehicle with an airbag module as specified in the preamble of claim 1.

[0002] A disclosed passenger protection device in a motor vehicle withan airbag module which is mounted behind a wall area and contains atleast one folded airbag and at least one gas generator (DE 196 17 758C1) comprises a covered exit opening in the wall area which may beopened by application of pressure for the airbag which is opened afteractivation.

[0003] The exit opening is covered in this instance by a cover cap whichmay be lifted from a closed position to a clearing position permittingemergence of the airbag opening under pressure. In addition, a reboundstrap mounting is provided for the cover cap. The cover cap may in thisinstance be forced out of an airbag cover in the wall area enclosing thecover cap. In order to enlarge this opening predetermined yield linesare provided which extend more or less radially from the airbag exitopening in the wall area. The movement of a cover cap which has beenforced out and lifted is relatively uncontrolled in the area delimitedby the length of the rebound strap, as a result of which these covercaps may exhibit greater aggressive behavior toward a vehicle passenger.A relatively large opening diameter is required for the purpose ofairbag emergence, a diameter which is unimpeded to the greatest extentpossible, with the result that the removable cover cap will accordinglyalso be relatively large in diameter. Consequently, freedom ofconfiguration is constrained toward smaller diameters for the cover capssuch as are required, for example, in the steering wheel hub area in thecase of a steering wheel airbag. But it is also to be noted in thisconnection that smaller lift-off cover caps may additionally exhibitmore aggressive behavior toward a passenger.

[0004] A similar design is also disclosed by DE 40 10 767 A1.

[0005] DE 197 49 914 A1 also discloses a passenger protection device ona steering wheel of a vehicle with a steering wheel airbag module, thesteering wheel airbag module being mounted behind a hub cover of asteering wheel hub and containing at least one folded steering wheelairbag and at least one gas generator. The hub cover has a stationarycenter area as first wall area around which is mounted a second wallarea immediately adjacent to an edge connecting area. A predeterminedcircular yield line mounted concentrically with the stationary centerarea is provided in the second wall area, spaced a certain distance fromthe stationary center area and thus spaced a certain distance from theedge connection area. In addition, there is formed in the second wallarea a plurality of radially extending predetermined opening lines whichextend radially from the edge connection area of the second wall areainto an area over the predetermined opening line moving in a circle, sothat individual flap areas are formed on the hub cover. In the event ofairbag activation, the airbag inflating in a circle around thestationary center area exerts pressure from below on the second wallarea such that the individual predetermined opening lines move apart andso clear an annular gap around the stationary center area for airbagemergence. The second wall area moves apart in such a way that theannular gap is formed at a certain distance from the stationary centerarea more or less in the area of the predetermined opening line by theindividual opening flap areas.

[0006] With a design such as this a removable cover flap may beeliminated, since the wall area enclosed in the annular gap may remainstationary as center area. The hub cover is in this instance made of aplastic material making it possible to provide the individualpredetermined yield points of the predetermined opening lines on theinside of the cover so as not to be visible from the exterior. However,a design such as this of the hub cover with predetermined opening linesis possible only with certain plastic materials. In particular, in thecase of high-quality vehicle interior equipment the desire still existsfor use of other high-quality materials such as leather, textile orfabric material, etc. in conjunction with the design of steering wheelcovers and so hub covers. However, a problem arises with suchhigh-quality materials, in that in this instance predetermined openinglines or predetermined yield points are undesirably visible fromoutside, that is, from the visible side. This leads to an impressionaltogether of lower quality and so lowers the overall opticalimpression, especially in the case of high-quality vehicle interioraccouterments. In addition, the cover is possibly also damaged as aresult. Consequently, a design such as this of a passenger protectiondevice on a steering wheel with such predetermined opening lines isscarcely workable when use is made of the materials in question for huband steering wheel covers and so the potential for their use can only berestricted.

[0007] In addition, such production of predetermined opening lines bymeans of individual predetermined yield points also entails considerablecost for production engineering, so that production is also relativelyexpensive in the aggregate.

[0008] A passenger protection device on a steering wheel of a vehicle inwhich a plurality of different materials, in particular alsohigh-quality leather and/or fabric materials, may be used as hub and/orsteering wheel covers is disclosed in generic WO 97/43783. In the caseof this passenger protection device a steering wheel airbag module ismounted behind a hub cover of a steering wheel hub and has at least onefolded steering wheel airbag and at least one gas generator. The hubcover has a stationary center area as first wall area around which ismounted a second edge area with immediately adjoining edge connectionarea. In the event of airbag activation an annular gap may be formedaround the stationary center area in the second wall area, the steeringwheel airbag being correspondingly circular with a tubular areaassociated with the annular gap and emerging from it when the bag is inthe inflated state. The annular gap may in the event of airbagactivation be formed immediately around the stationary center areathrough expansion and/or opening at least of the edge connection area ofthe second wall area.

[0009] Specifically, in this instance the edge connection area of thesecond wall area rests against the stationary center area from below,that is, the edge connection area of the second wall area is overlappedby an edge area of the stationary center area. When the airbag isactivated, the inflating airbag presses the second wall area, andespecially the edge connection area, outward and so away from theconfiguration connection below the stationary center area for clearingof the annular gap. In this configuration, if the passenger protectiondevice has not been activated the danger exists that as a result ofimproper treatment, such as pushing on the area of the second wall area,the second wall area will be raised by the stationary center area andundesired access to the area of the airbag or the airbag module iscleared as a result. In addition, a certain undesirable danger ofmanipulation is also created, especially if the second wall area is madeof a material which is relatively flexible.

[0010] A similar configuration with the same disadvantages is alsodisclosed in U.S. Pat. No. 4,828,286, in which the edge connection areaof the second wall area rests on the edge area of the stationary centerarea.

[0011] Consequently, the object of the invention is further to develop ageneric passenger protection device in such a way that the danger ofundesired lifting of the edge connection area from the stationary centerarea may be prevented when the passenger protection device is in theunactivated state.

[0012] This object is attained by means of the characteristics specifiedin claim 1.

[0013] According to claim 1, the edge connection area of the second wallarea is clamped on the stationary center area when the passengerprotection device has not be activated, it being possible for the edgeconnection area to be extracted by the inflating airbag from theclamping and be expanded and/or opened around the stationary centerelement by the inflating airbag for formation of the annular gap.

[0014] The disadvantages indicated above can be prevented to advantageby such clamping of the edge connection area when the passengerprotection device on the center area has not been activated, since theedge connection area is as a result retained on the stationary centerarea. The clamping is designed so that the edge connection area may beextracted from the clamping by the inflating airbag when the passengerprotection device has been activated.

[0015] In addition, no predetermined opening lines or predeterminedyield points need be produced with such a design, so that the productioncost is reduced and accordingly simple and low-cost production is on thewhole possible. In particular, however, materials such as leather and/orfabrics creating the impression of high quality may be used inconjunction with hub and steering wheel covers without impairment of orpossibly even damage to the visual aspect of such covers in an opticallyunseemly manner, something which is incompatible especially with therequirements set for high-quality vehicle interior accouterments. In apreferred embodiment the second wall area is accordingly designed atleast in part as a leather cover.

[0016] In one specific embodiment in this context, the stationary centerarea, preferably designed to be bending resistant and dimensionallystable, as specified in claim 2, with a center edge area, rests on theedge connection area of the second wall area. The edge connection areais clamped between the center edge area and a clamping elementpreferably mounted so as to be bending resistant and dimensionallystable. In a configuration such as this the edge connection area isextracted from the clamping by the inflating airbag, at least the edgeconnection area being expandable and/or openable for formation of theannular gap around the stationary center element.

[0017] An especially effective clamping is obtained by means of thecharacteristics specified in claim 3, which specifies that the clampingelement supports or clamps the edge connection area as viewed from theairbag module by means of a clamping element edge area.

[0018] In one especially preferred specific embodiment the stationarycenter area as specified in claim 4 is laminar in form and may befastened by a central and more or less vertically oriented pin extensionon the airbag module, preferably on the diffusor. The clamping elementis troughlike, with a tub edge as clamping element edge area and has acentral opening through which the pin extension of the stationary centerarea extends, preferably so as to be positive locking. A configurationsuch as this may be produced by simple and cost-effective means whichensures high operational reliability.

[0019] In one alternative embodiment the preferably bending resistantand dimensionally stable stationary center area as specified in claim 5has a circumferential groove on a circumferential surface into which theedge connection area of the second wall area may be clamped, in such away that the edge connection area may be extracted by the inflatingairbag from the circumferential groove and may be expanded and/or openedaround the center element by the inflating airbag for formation of theannular gap. It is advantageous that a reduced component cost isobtained in this instance, since the stationary center area is used in adual function at the same time also for fastening the edge connectionarea or snapping it in.

[0020] Stationary center areas such as this may be produced, forexample, integrally with ornamental elements. As an alternative it isalso possible, however, to snap, crimp, or glue separate emblems to thestationary center area.

[0021] Claim 6 specifies that the stationary center area rests on theairbag module housing, preferably a diffusor, for orientation with feet,the stationary center area being fastenable by way of a central and moreor less vertically oriented pin extension on the airbag module housing,preferably on the diffusor, preferably by threaded connection. Properseating of the stationary center area by simple means is ensured also inthe case of an edge connection area snapped into the circumferentialarea of the stationary center area.

[0022] Theoretically the stationary center area may be produced byvarious ways and means, preferably, however, in the form of a cast orextruded part.

[0023] It is advisable for the first wall area, preferably a stationaryornamental cap, forming the stationary center area surrounding theannual gap to be rigidly connected to the subjacent airbag modulehousing, as specified in claim 7. Depending on the actual circumstances,at least one part of a housing wall of the airbag module could also formthe stationary center area as a visible surface. In particular,additional configuration potential results from a combination of visiblesurfaces with ornamental caps and/or emblems.

[0024] For the sake emergence of the airbag as unimpeded as possible, itis advisable, as specified in claim 8, for the annular gap to be more orless circular in shape so that it encloses a first wall areacorrespondingly more or less circular in shape. In this way such adesign may be adapted to advantage to a conventional basic hub shape ofa steering wheel. Strictly speaking, however, a rectangularconfiguration of the annular gap is also possible, the annular airbagthen being correspondingly rectangular in shape.

[0025] Claim 9 specifies that a cover-like central ornamental cap mayalso be included for the sake of specific airbag exit behavior, in thatan edge area of the ornamental cap could be folded upward, optionally bythe airbag forcing its way out, for the purpose of enlargement of theannular gap and of formation of a guide surface.

[0026] According to claim 10, an exit annular channel is formed for theairbag which is bounded by channel walls. The exit behavior of theairbag may also be affected in a predetermined manner by imparting aspecific shape to these channel walls. For example, tapering of theannular exit channel toward the annular gap has the effect of delayingemergence of the airbag.

[0027] Claim 11 specifies that the stationary center area is in the formof a stationary ornamental cap. The annular gap may be relative large insize for purposes of unimpeded airbag exit, so that a relatively smallornamental cap is possible, this leaving free spaces for design. Thus,because of its stationary mounting the ornamental cap may now be used toadvantage for mounting of operating and design elements such as pushbuttons, wooden trim, or even a video screen. In addition, the conceptfor mounting the airbag module advantageously no longer depends on thecap design, but may be freely selected, for example, by an ancillarycompany, the airbag being folded, for example, into the ornamental capor into the gas generator carrier. Another free structural and designspace is thereby created by such a configuration.

[0028] In order to effect a certain amount of protection in the event ofa secondary collision, claim 14 specifies that the stationary centerarea, preferably an ornamental cap, have insulating material, preferablya foam material, placed beneath it.

[0029] The invention is discussed in greater detail in what follows withreference to a drawing, in which

[0030]FIG. 1 shows a schematic top view of a hub cover with airbagunfolded,

[0031]FIG. 2 a schematic cross-sectional view along line A-A of FIG. 1,

[0032]FIG. 3 a schematic cross-section through a first, specificembodiment of a passenger protection device, and

[0033]FIG. 4 a schematic cross-section through another embodiment of apassenger protection device claimed for the invention.

[0034]FIG. 3 illustrates a first, specific, embodiment of a hub cover 18of a steering wheel 2 in which the stationary center area forming thefirst wall area of the hub cover 18 is in the form of an ornamental cap21 which may be rigidly connectible to a diffusor 19 of an airbag module20 and is preferably bending resistant and dimensionally stable. Theornamental cap 21 rests by a center edge area 22 on an edge connectionarea 23 of a second wall area 24 of the hub cover 18. The edgeconnection area 23 is clamped between the center edge area 22 and astationary and preferably bending resistant and dimensionally stableclamping element 25, such clamping element 25 supporting the edgeconnection area 23 as seen from the direction of the airbag module 20 bya clamping element edge area 26. The clamping element 25 is in thisinstance more or less troughlike in design, while the ornamental cap 21is laminar in form and is fastened by a central and more or lessvertically oriented pin extension 27 to the diffusor 19. The clampingelement 25 also has a central opening through which the pin extension 27of the ornamental cap 21 extends, preferably effecting positive locking.

[0035] In the event of airbag activation air is blown into a circularairbag 28 by way of the diffusor, as is indicated schematically by thearrows in FIG. 3. The edge connection area 23 is extracted from theclamping between the ornamental cap 21 and the clamping element 25 bythe inflating airbag, the hub cover 18 being expanded and/or openedimmediately around the ornamental cap 21 in the edge connection area 23to form an annular gap 5, as is indicated here only by broken lines andvery schematically.

[0036]FIG. 4 illustrates another alternative embodiment which differsfrom that shown in FIG. 3 in that an ornamental cap 29 in this instancehas a circumferential groove 30 on a circumferential surface, a grooveinto which an edge connection area 31 of a second wall area 33 of a hubcover 32 is snapped or clamped. The ornamental gap 29 rests for thepurpose of orientation with feet 34, 35 on a diffusor 36 of an airbagmodule 37 and is detachably joined by a threaded connection to thediffusor 36 by way of a pin extension 38.

[0037] In the event of airbag activation the edge connection area 31 isin this instance extracted from the circumferential groove 30 by aninflating annular airbag 39, as a result of which the hub cover 32 inthe edge connection area 31 is expanded and/or opened immediately aroundthe ornamental cap 29 to form an annular gap, something indicated hereonly by broken lines and very schematically.

[0038] The inflated state of the airbag 28, 39 is illustratedschematically in a top view in FIG. 1, while FIG. 2 presents a schematicsection along line A-A. The central tubular area 11 of the airbag isadvantageously relatively small in diameter and, when the airbag hasbeen inflated, is closed again largely as a result of internal airbagpressure to a great extent by tubular walls striving toward each other,so that the protective function is performed just as it is with aconventional balloon-shaped air bag.

[0039] Because of its stationary mounting the ornamental cap 21, forexample, may be used to advantage for mounting of operating and designelements, such as pushbuttons, wooden trim, etc. For example, theornamental cap 21 may be used in this instance in its function of emblembacking for mounting a corporate logo; such logo may either beintegrated into the ornamental cap 21 or may be glued onto or snappedinto the ornamental cap 21 as a separate component.

[0040] In addition, but as is not illustrated here, there may be formedbelow the annular gap freed in the event of airbag activation an annularexit channel which is defined by channel walls. The exit behavior of theairbag may be influenced at the same time in a predetermined manner byspecific shaping of these channel walls. For example, a conicalnarrowing may be provided in the annular exit channel.

1. A passenger protection device on a steering wheel of a vehicle with asteering wheel airbag module, the steering wheel airbag module beingmounted behind a hub cover and containing at least one folded airbag andat least one gas generator, the hub cover having a stationary centerarea as first wall area about which is mounted a second wall areadirectly joined to the first wall area by an edge connection area, itbeing possible for an annular gap to be formed around the stationarysecond area in the second wall area in the event of airbag activation,the steering wheel airbag being correspondingly annular in form with atubular area associated with the annular gap and emerging from such gapwhen the airbag is in the inflated state, and it being possible for theannular gap to be formed immediately around the stationary center areain the event of airbag activation as a result of expansion and/oropening of at least the edge connection area of the second wall area,characterized in that the edge connection area (23; 31) of the secondwall area (33) is clamped to the stationary center area (21; 29) whenthe passenger protection device has not been activated, and in that theedge connection area (23; 31) may be extracted from the clamping by theinflating airbag (28) and may be expanded and/or opened around thestationary center area (21; 29) for formation of the annular gap (5). 2.The passenger protection device as claimed in claim 1, wherein thestationary center area (21) rests by a center edge area (22) on the edgeconnection area (23) of the second wall area (24) and wherein the edgeconnection area (23) is clamped between the center edge area (22) and aclamping element (25).
 3. The passenger protection device as claimed inclaim 2, wherein the clamping element (25) clamps the edge connectionarea (23) as viewed from the direction of the airbag module (20) to aclamping element edge area (26).
 4. The passenger protection device asclaimed in claim 2 or claim 3, wherein the stationary center area (21)is laminar in form and may be fastened to a central and more or lessvertically oriented pin extension (27) on the airbag module (20),preferably on the diffusor (19), and the clamping element (25) istroughlike with a trough edge as clamping element edge area (26) and hasa central opening through which the pin extension (27) of the stationarycenter area (21) extends, preferably effecting positive locking.
 5. Thepassenger protection device as claimed in claim 1, wherein thestationary center area (29) has on a circumferential surface acircumferential groove (30) into which the edge connection area (31) ofthe second wall area (33) may be snapped in such a way that the edgeconnection area (31) may be extracted from the circumferential groove(30) by the inflating airbag (39) and may be expanded and/or opened bythe inflating airbag (39) to form the annular gap around the centerelement (29).
 6. The passenger protection device as claimed in claim 1,wherein the stationary center area (29) rests on the airbag modulehousing, preferably a diffusor (36), for orientation with feet (34, 35)and wherein the stationary center area (29) may be fastened by way of acentral and more or less vertically oriented pin extension (38) on theairbag module housing, preferably on the diffusor (36), preferably bymeans of a threaded connection.
 7. The passenger protection device asclaimed in one of claims 1 to 6, wherein the first wall area forming thestationary center area (21; 29) and surrounded by the annular gap (5) isrigidly connected to the airbag module housing (9) and/or wherein atleast one part of a housing-wall of the airbag module forms thestationary center area (21; 29) as visible surface.
 8. The passengerprotection device as claimed in one of claims 1 to 7, wherein theannular gap (5) is more or less circular in form and encloses a firstwall area more or less in the form of a circular surface as stationarycenter area (21; 29).
 9. The passenger protection device as claimed inone of claims 1 to 8, wherein the annular gap (5) which may be formed inthe event of airbag activation in the second wall are (24; 33) isbounded by the edge area of an ornamental cap preferably in the form ofa cover as stationary center area (8), in such a way that this edge areamay be bent outward by an airbag forcing its way out of the annular gap(5) to enlarge the annular gap and to form a guide surface.
 10. Thepassenger protection device as claimed in one of claims 1 to 9, whereinthere is formed below the annular gap (5) an annular exit channel whichis bounded by channel walls the shape of which is adapted to apredetermined exit behavior of the airbag.
 11. The passenger protectiondevice as claimed in one of claims 1 to 10, wherein the stationarycenter area (21; 29) is formed by a stationary ornamental cap.
 12. Thepassenger protection device as claimed in one of claims 1 to 11, whereinthere is introduced below the stationary center area, preferably anornamental cap, an insulating material, preferably a foam materialand/or wherein the second wall area (24; 33) is at least in part in theform of a leather cover.